Cutaneous leiomyomas (leiomyosarcomas) are smooth muscle tumors that occur single or as multiple lesions. They usually arise from the arrector pili muscles (piloleiomyomas) and less commonly from the muscle of veins (angioleiomyomas). This report describes histologic and immunohistochemical features of one cutaneous piloleiomyoma and two angioleiomyosarcomas. Three 7-12-year-old female dogs were presented with single or double cutaneous nodules. Histologically, the neoplastic masses were composed of densely or loosely arranged interlacing bundles. The neoplastic cells were ovoid to elongate, and had eosinophilic cytoplasms and perinuclear cytoplasmic vacuolation. Nuclei were central to eccentric, cigar shaped, oval to elongate. In two cases high mitotic index in high power field, multifocal necrosis and local invasion were also noted. Masson's trichrome and van Gieson staining revealed muscle origin tumors in these cases. Immunohistochemically, the tumor cells were strongly positive for smooth muscle actin. In our best knowledge, this is the first report of cutaneous smooth muscle tumors in dogs in Korea.

Discoid lupus erythematosus (DLE) is an immune-mediated skin disease which requires histopathology and immunohistopathology in both dogs and humans. A 10-month-old, intact female Alaskan Malamute presented for depigmentation, swelling, alopecia, erythema, and crusting on the bridge of the nose and the nasal planum. Cytological examination of nasal lesions revealed numerous cocci and neutrophils. Histopathological features included of infiltration of mononuclear cells at the dermoepidermal junction. Direct immunofluorescence tests and immunohistochemistry exhibited positive IgG, IgM, IgA, CD3, CD18, and CD 79a on the epidermal basement membranes and around adnexal glands. This case indicates both T cells and B cells are related to mechanism of canine DLE. This case report describes advanced diagnostic tests and clinical outcome with immume suppressive therapy in a rare juvenile canine DLE case.